Background

The ability of dendritic cells (DCs) to regulate adaptive immunity makes them interesting cells to be used as therapeutic targets modulating alloimmune responses. Mycophenolic acid (MPA) is an immunosuppressor commonly used in transplantation, and its effect on DCs has not been fully investigated.

Methods

Monocyte-derived DCs were obtained from healthy volunteers and cultured for 7 days. Cells were treated with MPA on day 2 and matured by lipopolysaccharide (LPS) stimulation. Functionality of mature DC (mDCs) was evaluated by allogeneic mixed lymphocytes reaction. Surface expression of maturation markers (CD40, CD83, CD86, and ICAM-1) was analyzed in both immature DCs (iDCs) and mDCs by flow cytometry. To assess transcriptional regulation and protein subcellular location, RT-PCR and confocal microscopy were used, respectively.

Results

MPA decreased surface expression of all maturation markers in mDCs and significantly abrogated DCs-induced allogeneic T-cell proliferation after MPA pre-treatment. In iDCs, the reduced surface protein expression after MPA paralleled with mRNA downregulation of their genes. In mDCs, the mRNA levels of ICAM-1, CD40 and CD83 were enhanced in MPA-treated mDCs with an increase in the expression of CD83 and ICAM-1 near the Golgi compared to non-treated mDCs. In contrast, mRNA levels of CD86 were diminished after MPA treatment.

Conclusions

The reduced surface markers expression in mDCs exerted by MPA produced a decline in their capacity to activate immune responses. Moreover, the inhibition of guanosine-derived nucleotide biosynthesis by MPA treatment leads to DC maturation interference by two mechanisms depending on the marker, transcriptional downregulation or disrupted intracellular protein trafficking.

中文翻译：

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霉酚酸干扰树突状细胞成熟表面标记物的转录调控和蛋白质运输

 背景

树突状细胞 (DC) 调节适应性免疫的能力使其成为有趣的细胞，可用作调节同种免疫反应的治疗靶点。霉酚酸（MPA）是移植中常用的免疫抑制剂，其对 DC 的影响尚未得到充分研究。

 方法

单核细胞来源的 DC 取自健康志愿者并培养 7 天。第 2 天用 MPA 处理细胞，并通过脂多糖 (LPS) 刺激使其成熟。通过同种异体混合淋巴细胞反应评估成熟 DC (mDC) 的功能。通过流式细胞术分析未成熟 DC (iDC) 和 mDC 中成熟标志物（CD40、CD83、CD86 和 ICAM-1）的表面表达。为了评估转录调控和蛋白质亚细胞定位，分别使用了 RT-PCR 和共聚焦显微镜。

 结果

MPA 预处理后，可降低 mDC 中所有成熟标志物的表面表达，并显着消除 DC 诱导的同种异体 T 细胞增殖。在 iDC 中，MPA 后表面蛋白表达减少与其基因 mRNA 下调同时发生。在 mDC 中，与未处理的 mDC 相比，MPA 处理的 mDC 中 ICAM-1、CD40 和 CD83 的 mRNA 水平增强，高尔基体附近的 CD83 和 ICAM-1 的表达增加。相反，MPA 处理后 CD86 的 mRNA 水平降低。

 结论

MPA 导致 mDC 表面标志物表达减少，导致其激活免疫反应的能力下降。此外，MPA 处理对鸟苷衍生的核苷酸生物合成的抑制会导致 DC 成熟受到两种机制的干扰，这两种机制取决于标记物：转录下调或细胞内蛋白质运输中断。